Kiln Wash Application Problem
- September 7, 2011 at 12:10 am #9303
I just purchased two new ceramic molds and tried to apply kiln wash. I have very little experience with the wash since I use Thinfire paper almost exclusively when firing. I mixed the wash as directed and started to brush it on. It doesn’t seem to want to cover the mold. I applied in one direction and it left a few bare spots and then when I switched directions, the first layer of kiln wash started to lift off. This happened every time I changed directions, so there are several places on the mold that are still bare. I even waited 15 minutes or so between layers and still the problem persisted.
I have watched several YouTube videos showing how to apply the wash and my technique is the same as all the demonstrations I have viewed. I tried using several different types of brushes – that made no difference.
One mold is a slumping mold and the wash just runs down the side to the bottom but doesn’t coat in some places. The other mold is an earring casting mold and when I try to wash the insides of the cavities, the wash comes off the edges of each cavity.
The kiln wash I’m using came with my kiln. It’s Hotline Shelf Primer and I assume it’s good since the manufacturer recommends it by including it with the kiln.
I’m stumped. Any suggestions as to why this is happening and what I can do to fix it?
BarbSeptember 8, 2011 at 2:24 am #12197wordanaParticipant
Perhaps it’s related to your brush. You’ll have the most success with a haik brush:
Dana W.September 10, 2011 at 9:07 pm #12198glassbymargotParticipant
I had a similar problem with a shelf once. I fired the shelf in my kiln to1500 degrees F. Whatever was on the shelf preventing it from taking on the kiln wash burned off. Not sure if this will help but but may be worth a try.September 10, 2011 at 9:30 pm #12199
What schedule did you use? Did you do AFAP to 1500, hold for 5-10 minurtes, and then AFAP back down?
Thanks for you suggestion.
BarbSeptember 11, 2011 at 7:42 am #12200Stephen RichardParticipant
AFAP is not recommended for ceramic moulds. Firing to about 720C (about 50C above the maximum slumping temperature) will be enough. Since I would be firing any glass on a mould no faster than 150C/hr, that is the rate i would use all the way up to 720C. No soak is necessary. Set the controller to “off” and let the kiln cool on its own from 720C down.
It is worth noting that in slip cast moulds there often is a “hard” spot where the liquid slip first contacts the mould. Normally, although it appears there is no kiln wash on the spot, there is enough to separate the glass from the mould. However the advice to fire the mould first before putting kiln wash on is a good one.
Stephen RichardSeptember 11, 2011 at 5:04 pm #12201
Thanks for the tips! I will try the firing the mold and see if that solves the problem.
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